[ARTICLE] Weight compensation characteristics of Armeo®Spring exoskeleton: implications for clinical practice and research – Full Text

Abstract

Background

Armeo®Spring exoskeleton is widely used for upper extremity rehabilitation; however, weight compensation provided by the device appears insufficiently characterized to fully utilize it in clinical and research settings.

Methods

Weight compensation was quantified by measuring static force in the sagittal plane with a load cell attached to the elbow joint of Armeo®Spring. All upper spring settings were examined in 5° increments at the minimum, maximum, and two intermediate upper and lower module length settings, while keeping the lower spring at minimum. The same measurements were made for minimum upper spring setting and maximum lower spring setting at minimum and maximum module lengths. Weight compensation was plotted against upper module angles, and slope was analyzed for each condition.

Conclusions

Understanding the impact of different settings on the Armeo®Spring weight compensation should help define best clinical practice and improve fidelity of research.

Presented in part at the 9th World Congress of Neurorehabilitation, Philadelphia, PA, May 10–13, 2016

Methods

Setup and instrumentation

The net static force applied to a load cell was measured to infer the weight compensation provided by the springs at different settings in the sagittal plane (Fig. 1). Both shoulder and elbow joints of the exoskeleton were locked to maintain the upper and lower modules in the horizontal plane. The load cell was connected near the elbow joint and kept vertical to the exoskeleton. To accommodate the direction of spring forces exerted on the load cell, the instrumentation was positioned below the exoskeleton to measure unloading and above the exoskeleton to measure loading.

Fig. 1 Experimental Setup

The load cell (Omega LCCB200) was connected to a signal conditioner (Daytronic 3270). The output voltage was fed into an analog-to-digital converter (National Instruments USB-6008) and recorded in a custom LabView program for 10 s per condition (sample rate 1 kHz). The load cell was calibrated to derive a linear formula for converting voltage into weight…